You're correct, Wade, but to clarify, an applicant does not apply for an “international” patent by filing an application under the PCT. There is no central authority with the power to grant an "International" or "world patent". The World Intellectual Property Organization (WIPO) administers the PCT filing process which produces a single patent application that has been vetted for compliance with filing formalities and that has undergone a preliminary search and evaluation. This single application can then be transmitted to the national patent offices of as many PCT member countries as the applicant chooses, for filing as a "national-phase" application in that country or countries. The PCT thus streamlines and consolidates the process of seeking patent protection in more than one country into a single series of steps and a single set of preliminary requirements.
The PCT application process generally gives the applicant an additional 18 months to consider whether and in which country or countries to pursue patent protection. If the applicant first filed a patent application in the United States, then filed a PCT application within 12 months of the U.S. filing, the applicant would generally have an additional 18 months to nationalize the PCT application in the foreign country or countries in which the applicant desired patent protection. Once the application is nationalized in a particular country, the application will be examined under the local laws of each country to determine whether a patent should be granted.
At a bare minimum, I would estimate the costs of the initial PCT filing fees alone for a small entity to be in the area of $5,000 USD. Additional fees, if required, and associated legal fees could easily double or triple that. By far, the most expensive aspect of international patent procurement is the national-phase cost, which includes the fees paid to each national patent office for entrance into the national phase and during the patent prosecution process, the legal fees of local attorneys or agents to obtain a national patent, and the fees to the national patent office to maintain the granted patent in force.